Make NTP request more robust. #7
Open
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Previously, only the memory for the NTP header was declared and set. Actually, apart from the headers, the rest of the NTP packet (48 bytes) contains timestamps. Those timestamps are interpreted by the NTP server as offsets from their time and are used to calculate the new time. Therefore, if the rest of the packet is not zero, a wrong time is received. By reserving memory only of the header and sending 48 bytes nonetheless we send as timestams whatever values the microcontroller has on the stack. If the stack content is not zero, we receive back a garbage timestamp. This commit fixes this issue and also make the code a bit more readable by moving some magic constants in the header file.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Previously, only the memory for the NTP header was declared and set.
Actually, apart from the headers, the rest of the NTP packet (48 bytes)
contains timestamps.
Those timestamps are interpreted by the NTP server as offsets from their time
and are used to calculate the new time. Therefore, if the rest of the
packet is not zero, a wrong time is received.
By reserving memory only of the header and sending 48 bytes nonetheless
we send as timestamps whatever values the microcontroller has on the stack. If
the stack content is not zero, we receive back a garbage timestamp.
This commit fixes this issue and also make the code a bit more readable
by moving some magic constants in the header file.
This code has been tested on an ESP8266 and works correctly.